1. Field of the Invention
The present invention relates to an electronic keyboard instrument, such as an electronic piano, and more particularly to an electronic keyboard instrument having a speaker box accommodating speakers and disposed under an instrument body including a keyboard, etc.
2. Description of the Related Art
Conventionally, as an electronic keyboard instrument of the above-mentioned type, there has been known one disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2000-81885. The electronic keyboard instrument has an instrument body accommodating a keyboard, etc. and a speaker box accommodating a speaker and disposed under the speaker body. The instrument body is formed into a box shape by connecting a keybed, a top board, left and right arms, and a backboard to each other. The keybed has an opening formed therein at a location corresponding to the speaker.
The speaker box is an unitary assembly formed by combining a bottom board, a top board, a front board, and a backboard each extending in a left-right direction. The speaker is mounted on the bottom board, and an opening is formed in the bottom board such that the sound emission surface of the speaker faces the opening. The top board is formed with a plurality of communication holes.
The speaker box constructed as above is fixed to an instrument stand in a state sandwiched between the left and right side boards of the instrument stand. The instrument body is placed on the instrument stand and fixed to the same, whereby the electronic keyboard instrument is assembled. Musical sound generated by key depression is output from the sound emission surface of the speaker and emitted from the opening formed in the bottom board of the speaker box. The musical sound is also output from other portions of the speaker and emitted from the communication holes of the top board of the speaker box and the opening of the keybed.
However, in this conventional electronic keyboard instrument, the keybed having the keyboard, etc. placed thereon has its outer peripheral portions connected to the arms and the backboard, and is supported on the instrument stand. Therefore, there is a fear that the keybed is largely warped due to a large load e.g. from the keyboard, which can cause degradation of the appearance of the keyboard and malfunction of keys. Further, since the keybed is formed with the opening for guiding musical sound output from the speaker into the instrument body, the rigidity of the keybed is reduced, which causes a further increase in warpage of the keybed.
Furthermore, the instrument body and the speaker box are formed separately from each other, the back boards of these have to be mounted separately. For this reason, two separate backboards appear on the rear surface of the electronic keyboard instrument, and the number of screws for fixing the backboards is increased, which causes degradation of the appearance of the electronic keyboard instrument. In addition, since the backboards are in contact with the keybed, vibration of the speaker box caused by output of sound from the speaker is transmitted from the keybed to the backboards, which can generate noise, such as rattle noise. Therefore, it is required to take a soundproofing measure e.g. by providing a vibration-proof cushion between the keybed and the backboards.